1. Field of the Invention
The present invention relates to a method of blowing a synthetic resin into a furnace and an apparatus therefor.
2. Description of the Related Art
The quantity of waste synthetic resins such as plastics as industrial waste and general garbage has recently been increasing, and disposal thereof has become an important social issue. Particularly, plastics, which is a macromolecular hydrocarbon compound, produces a high calorific value during combustion, and cannot be disposed of in a large quantity because of damage to an incinerator upon incineration, so that it is the current practice to dump most of waste plastics onto a reclamation site for waste. However, the dumping of plastics is not desirable from the environmental point of view, and there is an increasing demand for development of a quantity disposing method thereof.
Under such circumstances, methods using synthetic resins such as plastics as an auxiliary fuel for blast furnace are disclosed in European Unexamined Patent Publication No. 0622465A1 and Japanese Patent Publication No. S51-33493. These methods comprise blowing milled synthetic resins as a fuel into a blast furnace through tuyeres: the former method, for example, sets forth substantial conditions of the milled synthetic resin to be blown into the furnace including a particle diameter within a range of from 1 to 10 mm and a bulk density of at least 0.35.
As a result of repeated experiments and studies, however, the present inventors found the existence of the following problems involved in the use of synthetic resins such as plastics (hereinafter the description will be based on xe2x80x9cplasticsxe2x80x9d as a typical example) as a blown fuel for a blast furnace.
Plastics rejected as industrial waste or general garbage, when viewed in terms of form, are broadly divided into lumpy plastics taking a plate shape in general and film-shaped ones. The latter ones, film-shaped plastics, account for a considerable part among rejected plastics. However, because of very low transferability and fluidity of milled film-shaped plastics, there is a serious problem in handling when using them as a fuel. More specifically, when blowing plastics into a blast furnace as a fuel, it is the usual practice to cut plastics stored in a storage silo and pneumatically feed cut plastics into the blast furnace. Because of a very low fluidity of film-shaped plastics, milled plastics containing much film-shaped plastics easily produce bridges (scaffolding) in the storage silo, and troubles involving inability to cut out milled plastics in a constant quantity from the storage silo occur frequently. Further, film-shaped plastics clog the cutting port of the storage silo or the interior of a pneumatic feed pipe (particularly at bends and proximity of valves), leading to a serious problem of frequent occurrence of troubles preventing pneumatic feed to the blast furnace.
Unless these problems are overcome, therefore, it is practically impossible to use film-shaped plastics as a fuel to be blown into a blast furnace or the like. In view of the present circumstances of film-shaped plastics accounting for a major portion of waste plastics as a whole, it is clear that advantages of quantity disposal and effective utilization of waste plastics would be lost unless it is made possible to use film-shaped plastics.
In order to blow plastics as a fuel into the blast furnace, furthermore, it is necessary to use milled plastics to ensure a sufficient combustion property. There is however a limitation on the particle diameter acceptable for milling in terms of treatment cost. A particle diameter within a range of from about 1 to 10 mm is therefore a limit for granulation as is shown in the conventional art. When using lumpy plastics milled to this particle diameter, a sufficient combustion property may be unavailable within the blast furnace. As a result, unburned plastics adhere to each other in the bed coke, thus seriously impairing permeability through the furnace, and may cause trouble in the blast furnace operation.
Milled lumpy plastics take an irregular and angular shape. Ones having a particle diameter of from 1 to 10 mm are therefore low in discharge property upon cutting out from a storage silo and in fluidity and transferability when pneumatically feeding to the blast furnace, leading to easy occurrence of clogging at the cutting port of silo or in the middle of the pneumatic feed pipe system.
It is therefore very difficult to use waste plastics as a fuel to be blown into a blast furnace in an industrial scale by any of the methods proposed by the conventional arts: simply milling plastics into a particle diameter of from 1 to 10 mm processing the same into granules having a high bulk density and blowing the same into the blast furnace.
The present invention has an object to provide a method of blowing synthetic resins, which permits supply of waste synthetic resins as a blown fuel into a furnace, irrespective of the form thereof, and allows improvement of transferability and combustion property of synthetic resins supplied to the furnace, and an apparatus therefore.
To achieve the above-mentioned object, the present invention provides a method of blowing a synthetic resin material into a furnace, comprising:
(a) a step of classifying synthetic resins into film-shaped synthetic resins and other non-film-shaped synthetic resins;
(b) a step of processing classified film-shaped synthetic resins into a first granular resin material;
(c) a step of crushing non-film-shaped synthetic resins and processing the same into a second granular synthetic resin material;
(d) a step of pneumatically feeding the first granular synthetic resin material and the second granular synthetic material; and
(e) a step of blowing the pneumatically fed first granular synthetic material and second granular resin material into a furnace.
The foregoing process of processing the film-shaped synthetic resins into the granular synthetic resin materials may comprise:
a step of melting or semi-melting the film-shaped synthetic resins by heat; and
a step of solidifying the film-shaped synthetic resins in a molten or semi-molten state.
The method of blowing the synthetic resin material into the furnace of the present invention may further comprise:
a step of separating and removing a chlorine-containing macromolecular resin material from the film-shaped synthetic resins, the film-shaped synthetic resins after separation and removal of the chlorine-containing macromolecular resin material being processed into a granular synthetic resin material in step (b); and
a step of separating and removing the chlorine-containing macromolecular resin material from the non-film-shaped synthetic resins, the separation and removal step being carried out after step (c).
In the method of the present invention, the classifying step, the step of processing the film-shaped synthetic resins and the step of processing the non-film-shaped synthetic resins may be as follows:
the classifying step may comprise classifying the synthetic resins into a film-shaped synthetic resin material, a solid synthetic resin material and a sheet-shaped synthetic resin material, the sheet-shaped resin material being an intermediate form between the film-shaped synthetic resin material and the solid synthetic resin material;
the step of processing the film-shaped synthetic resins may comprise: a step of crushing the film-shaped synthetic resin material into small film pieces; and a step of applying a melting and solidification/granulating treatment to the small film pieces, thereby preparing first synthetic resin particles;
the step of processing the non-film-shaped synthetic resins may comprise:
a step of crushing the solid synthetic resin material,
thereby preparing second synthetic resin particles;
a step of crushing the sheet-shaped synthetic resin material,
thereby preparing small sheet pieces having a maximum size smaller than the maximum size of the small film pieces; and
a step of supplying a melting and solidification/granulating treatment to the small sheet pieces,
thereby preparing third synthetic particles.
Further, the process of processing the non-film-shaped synthetic resins may comprise:
a step of supplying shredder dust produced during rejection of an automobile or a home electrical appliance;
a step of cutting or crushing the shredder dust;
a step of heating the crushed shredder dust to semi-melt or melt the same; and
a step of causing the semi-molten or molten shredder dust to contract and solidify into a granular form.
Blowing of the granular synthetic resin material into the furnace should preferably be accomplished by blowing the granular synthetic resin material having such a particle diameter as giving a terminal velocity higher than the flow velocity of gases discharged from the combustion zone formed at the tuyere nose in the lower part of the furnace.
The present invention further provides an apparatus for blowing a synthetic resin material into a furnace, comprising:
a first processing line for processing film-shaped synthetic resins into a granular synthetic resin material;
the first processing line comprising a granulating/solidifying unit for processing the film-shaped synthetic resins into the granular synthetic resin material through solidification after melting or semi-melting the same with heat;
a second processing line for processing non-film-shaped synthetic resins into the granular synthetic resin material;
the second processing line comprising a crushing unit crushing the non-film-shaped synthetic resins;
a primary storage silo for storing the granular synthetic resin material obtained in the first processing line and the second processing line;
a blowing station for pneumatically supplying the granular synthetic resin material supplied from the primary storage silo into the furnace; and
the blowing station comprising:
a secondary storage silo for storing the granular synthetic resin material supplied from the primary storage silo;
a blowing tank for receiving the granular synthetic resin material supplied from the secondary storage silo,
and pneumatically feeding the same to the furnace;
and means for continuously supplying the granular synthetic resin material from the blowing tank into a blowing port of the furnace.
Further, the apparatus of the present invention should preferably have the following components:
a separating unit for separating and removing chlorine-containing macromolecular resin materials from the film-shaped synthetic resins, arranged in the upstream of the granulating/solidifying unit in the first processing line; and
a separating unit for separating and removing chlorine-containing macromolecular resin materials from the non-film-shaped synthetic resins, arranged in the downstream of the crushing unit in the second processing line.
The present invention further provides a method of blowing synthetic resin material into a furnace, comprising:
a step of preparing a synthetic resin material having an average specific surface area of at least 50 m2/kg; and
a step of blowing the synthetic resin material from tuyeres of a shaft furnace for ironmaking.
It suffices for the synthetic resin material to contain at least 5 wt. % particles having a particle diameter of up to 1 mm and having an average specific surface area of at least 25 m2/kg.
The synthetic resin material may contain at least 3 wt. % particles of a foaming substance and having an average specific surface area of at least 20 m2/kg.
The present invention furthermore provides a method of blowing a synthetic resin material into a furnace, comprising:
(a) a step of determining the heat value of a synthetic resin material from the result of quality determination of the material when it is possible to determine quality of the synthetic resin material and mixing of impurities is not observed;
(b) a step of determining the heat value of a synthetic resin material by measuring by an usual measuring method when it is possible to determine quality of the synthetic resin material and mixing of impurities is observed;
(c) a step of determining the heat value of a synthetic resin material by measuring by an usual measuring method when it is impossible to determine quality of the synthetic resin material;
(d) a step of blending two or more kinds of synthetic resin materials with the use of heat values for these two or more kinds of synthetic resin materials as determined in steps (a) to (c) so as to give a prescribed heat value of a mixture comprising the two or more kinds of synthetic resin materials; and
(e) a step of blowing the blended synthetic resin materials from tuyeres of the furnace.
The method of charging a synthetic resin material into a furnace of the present invention comprises:
(a) a step of preparing a synthetic resin material as a blast furnace burden raw material;
(b) a step of preparing a granular sinter as a blast furnace burden raw material;
(c) a step of preparing a mixture of the synthetic resin material and the granular sinter; and
(d) a step of charging the mixture into an intermediate zone between the center and the wall of the blast furnace.